The present invention relates to an apparatus for the control and monitoring of a well head submerged in a liquid. It applies to the control of the opening or closing of submerged well head valves and in particular those of oil or gas well heads, as well as to the monitoring of these well heads.
For various reasons, the valves of submerged or immersed well heads must be openable or closable at all times and it must be possible, for production and safety reasons, to check said opening or closing. Generally the opening or closing of well head valves is controlled by electrovalves, which are themselves submerged and controlled by an electrical or electronic system or unit, which is also submerged. This electrical or electronic system is contained in a tight enclosure and is connected to a station on the surface of the liquid medium by an electric signal transmission line. This line transmits to the electronic system and to the electrovalves, the electric signals necessary for supplying them with power. It also supplies electric or electronic system control signals for controlling the opening or closing of the electrovalves, as well as test signals for the system. This line transmits to the surface station signals resulting from the test signals, as well as measuring signals relating to parameters concerning the monitoring of the operation of the well head, said signals being supplied by sensors.
The direct control of the opening or closing of the valves from a station located on the surface of the liquid medium and which transmits control signals to the electronic system by a transmission line, such as e.g. a cable, suffers from disadvantages. If the cable breaks, it is no longer possible to check the electrovalves and therefore the opening or closing of the well head valves. in known control and monitoring apparatuses, most of the control and monitoring operations are performed from the station on the surface of the liquid medium. The electronic or electric system for controlling the electrovalves in fact only serves as an interface making it possible to transmit valve opening or closing control instructions supplied by the station or for transmitting to the station the results of measurements performed by the sensors, said results being processed by a system within the station.
In the case of an incident detected on the basis of these results, in most known apparatuses it is only the actual station which controls the closing of the valves by signals transmitted by the line. This is a serious disadvantage, particularly in the case of the breaking of the line connecting the electronic system to the surface station. In the known apparatuses, the electronic system is not programmable and the controls are essentially transmitted from the surface. However, for the electronic systems of the known apparatuses, there are means making it possible to automatically act on the electrovalves in the case of a line break, but said means are not programmable.
Thus, the automatic closure of the valves can be brought about by a complete breaking of the line, but also by simple transmission incidents on said line and which are likened to a break.